This invention relates to the field of apparatuses for gel electrophoresis.
Gel electrophoresis is a process in which charged analyte molecules move through a gel matrix under the force of an electrical field applied across the gel. After electrophoresis, the analytes can be fixed in the solid gel and identified, as in analytical gel electrophoresis. Also, the analyte can be eluted from the gel and isolated for further manipulation, as in preparative gel electrophoresis. Polyacrylamide and agarose are two of the most popular matrix materials for use with biomolecular analytes, such as proteins and nucleic acids.
The gel matrix usually takes the form of a slab or a tube. Slabs are run either horizontally or vertically. In either case sample wells are created in the gel in a line across the width of the gel and the voltage gradient is applied orthogonally to this line through the length of the slab gel.
Gels can be cast in an open four-walled compartment that holds the gel until it sets, or between two plates. Horizontal agarose slab gels generally are cast in an open four-walled compartment. Vertical and horizontal polyacrylamide slab gels generally are cast in a space formed between two plates. Casting plates are generally made of glass or plastic. In both horizontal and vertical gels, sample wells are created by dipping a comb into the gelling solution and allowing the gel to set around the comb.
Apparatuses for running horizontal gels generally include compartments that include electrodes and that hold electrophoresis buffer. The gel is placed between the two compartments so that the buffer contacts two ends of the gel and can impart a voltage gradient across the length of the gel. The electrodes are connected to a power supply. Such apparatuses are commercially available.
The relative movement of analytes in different parallel lanes of a slab gel depends primarily on the evenness of the voltage across the width of the gel at any point along the gel's length. The voltage at any point on the gel depends, in part, on the thickness of the gel.
Pre-cast, vertical polyacrylamide gels are now a marketplace staple. However, horizontal gels, especially those no more than about 3 mm thick and having an area of less than about 100 cm.sup.2 have not yet found complete public acceptance. Gels may not have a uniform thickness and bubbles can form between the plates during the casting process. Also, during shipment, pre-cast horizontal polyacrylamide gels can tear or separate from the casting cassette. An example of an apparatus for horizontal gel electrophoresis is described in the Cosmo Bio catalog, number Mupid-2. The apparatus includes a horizontal electrophoresis cassette comprising two plates that loosely fit together and that have open front and back edges.